During operation, the emulsion pump constantly draws out the emulsion from a bottle, and simultaneously air is supplemented to the bottle to balance the pressure between inside and outside of the bottle so that the continuous drawing out of emulsion from the bottle can be assured. Such channel for the flow of air is referred to as “air channel”. In prior art emulsion pump as shown in FIG. 1, one or more holes are provided on the wall of the cylinder 1 (only one hole is shown in FIG. 1) to communicate the pressure between the inside and the outside of the bottle. However, the hole 2, while contributing to the balance of the pressure between the inside and the outside of the bottle, brings unfavourable or negative effect on the pump. For example, during the transportation, the emulsion in the bottle can easily enter into the cylinder 1 via the hole 2. At this time, the pressing head 3 of the emulsion pump is usually locked as shown in FIG. 1. Consequently, the emulsion which enters into the cylinder 1 will adhere on the piston rod 4. When the emulsion pump is activated, the piston rod 4 will go up past the cylinder lid 5 following the pressing head 3, thereby the emulsion which is now on the piston rod 4 will be exposed, and the so called phenomenon of “liquid creeping-up” occurs.
The phenomenon of the liquid creeping-up is not only unaesthetic, but also gives undesirable effect in use, therefore it must be overcome.
The purpose of the present invention is to provide an emulsion pump with an air channel preventing liquid entrance, which enable not only the pressure between the inside and the outside of the bottle to be balanced, but also can prevent emulsion from contacting the piston rod, thereby preventing the occurrence of the phenomenon of liquid creeping-up.